Name: concrete spread measured by flow table
Uploaded: 2024-11-07T14:48:28.000Z
Duration: 1 min 12 s
Channel: JoVE

Il test della tavola di flusso, utilizzato per trovare la lavorabilità del calcestruzzo e valutare il calcestruzzo altamente scorrevole, prevede un apparato costituito da una tavola di legno sormontata da una piastra di acciaio, con un peso totale di 35 libbre.
Una cerniera collega la tavola a una base, con ogni lato della tavola che misura 27,6 pollici.
Il pannello superiore è progettato per essere sollevato a un'altezza di 1,6 pollici e il tavolo ha segni specifici che guidano dove deve essere posizionato il cemento.
Un tronco di cono alto 8 pollici, con un diametro di base di 8 pollici e un diametro superiore di 5 pollici, è riempito di cemento. Viene compattato delicatamente, il calcestruzzo in eccesso viene rimosso e lo stampo del cono viene rimosso con cura dopo 30 secondi.
Il tavolo viene scosso 15 volte, con ogni scossa data a un intervallo di 4 secondi, provocando la diffusione del cemento.
La media dell'estensione di diffusione parallela ai due spigoli della tavola, misurata dopo la scossa di scossa, indica la lavorabilità del calcestruzzo, con valori specifici corrispondenti a lavorabilità media o alta.

prova della tavola a scosse

La prova della tavola a scosse è un metodo consolidato utilizzato per valutare la lavorabilità del calcestruzzo, particolarmente utile per valutare miscele di calcestruzzo altamente fluide. Questo test impiega un apparato costituito da una tavola di legno sormontata da una piastra di acciaio, che pesa complessivamente circa 16 chilogrammi. La tavola è collegata a una base tramite una cerniera e misura circa 70 centimetri su ciascun lato.


 Il calcestruzzo viene posizionato all'interno di uno stampo a tronco di cono alto 20 centimetri con un diametro di base di 20 centimetri e un diametro superiore di 12 centimetri. Il calcestruzzo viene compattato delicatamente, l'eccesso viene rimosso e lo stampo viene rimosso dopo 30 secondi.


 La procedura di prova prevede di scuotere il tavolo 15 volte a intervalli di 4 secondi sollevando la tavola superiore a un'altezza di 4 centimetri. Questa azione fa sì che il calcestruzzo si sparga dalla forma iniziale del cono. Dopo la scossa, l'entità della diffusione del calcestruzzo viene misurata parallelamente ai due bordi del tavolo. La diffusione media viene calcolata per valutare la lavorabilità del calcestruzzo. Valori specifici di diffusione vengono utilizzati per classificare la lavorabilità del calcestruzzo come media o alta. Questo test fornisce dati cruciali sulla capacità del calcestruzzo di scorrere e assestarsi sotto il proprio peso, riflettendo la sua idoneità per varie applicazioni edilizie in cui sono necessarie elevata fluidità e distribuzione uniforme.

Prova della tavola a scosse

Il test della tavola di flusso, utilizzato per trovare la lavorabilità del calcestruzzo e valutare il calcestruzzo altamente scorrevole, prevede un apparato costituito da una tavola di legno ...

Education

Didattica

JoVE Core

Civil Engineering

Ingegneria Civile

Unit 1

Unità 1

Fresh Concrete

Calcestruzzo fresco

KEY TERMS AND CONCEPTS

TERMINI E CONCETTI CHIAVE

Flow Table Test

concrete spread measured by flow table

The flow table test measures how far fresh concrete spreads, which helps assess workability. Workability means how easily concrete can flow and settle under its own weight. The method is useful for highly flowable concrete mixes.

The test uses a flow table made from a wooden board with a steel plate on top. Together, the parts weigh 35 pounds. The board is hinged to a base and measures 27.6 inches on each side. A truncated cone mold is also used. It is 8 inches high, with an 8-inch base diameter and a 5-inch top diameter.

The concrete is placed in the mold and gently compacted. Then the excess is cleared away. After 30 seconds, the mold is removed. The table is jolted 15 times at 4-second intervals by lifting the upper board to a height of 1.6 inches. This motion makes the concrete spread out from its cone shape.

After jolting, the spread is measured parallel to the two edges of the table. The average spread is then calculated. This value is used to judge the concrete's workability. The results can place the mix in medium or high workability categories. The test gives useful data for construction applications that need high fluidity and even distribution.

Concrete Spread Measured by Flow Table

workability of concrete

Concrete Flow and Compaction Factors

Concrete workability is the ease with which fresh concrete can be mixed, placed, compacted, and finished. It is an important property during construction because it affects how well the material moves into position and how easily it can be shaped. Workability depends on the internal friction within the mix and the resistance it meets from molds and reinforcements. When the ingredients resist one another, concrete moves less easily. The same is true when it has to pass around barriers in the...

factors affecting workability

Concrete Workability and Mix Design Factors

Concrete workability depends on mix design factors that change how easily the material can be mixed, handled, and finished. The mix needs enough flow so it can move and be placed without losing quality. Water is a key part of this because it acts as a lubricant between the ingredients. The amount of water needed can change with the aggregates, or the solid particles in the mix. Finer particles and angular, rough-textured aggregates need more water than smooth, rounded ones because they have...

segregation in fresh concrete

How Concrete Mixes Separate During Placement

Fresh concrete can separate during placement, which changes how the mix is spread and can weaken the finished structure. This separation is called segregation. It happens when the parts of the mix no longer stay evenly blended. Segregation often occurs when concrete moves too much inside a form. It can also happen when the mix is dropped from a great height or pushed through narrow paths with sharp turns. In these cases, the heavier coarse aggregate settles at the bottom, while lighter...

bleeding in fresh concrete

Bleeding Water and Laitance in Fresh Concrete

Bleeding in fresh concrete happens when water from the mix rises to the surface after placement. The solid parts of the mix do not hold all the water as they settle, so separation occurs and water collects on top. Engineers can measure the severity of bleeding by checking total settlement or by noting how much the concrete height drops per unit height. Bleeding can create weak spots inside the concrete. Rising water may get trapped under large aggregate particles or reinforcement bars, which...

slump test

Concrete Workability Check with Slump

The slump test checks the workability of fresh concrete. Workability means how easy the mix is to place and handle. The test uses a 12-inch-high truncated cone mold that narrows from eight inches at the base to four inches at the top. Before testing, the mold is fixed to a flat base and dampened. Concrete is added in three layers. Each layer is compacted 25 times with a steel tamping rod that is five-eighths of an inch in diameter and has a rounded end. This helps spread the concrete evenly...

compacting factor test

Concrete Workability by Compacting Factor

The compacting factor test measures the workability of concrete. Workability describes how easily concrete can move and fill a mold or form during construction. This test is especially suitable for concrete mixes with aggregates up to one and a half inches in size. The setup uses specialized equipment with two truncated cone-shaped hoppers and a cylinder. All of the inside surfaces are polished to reduce friction. Concrete is first placed into the upper hopper without any compaction. Then the...

vebe test

Concrete Workability with the Vebe Test

The Vebe test measures the workability of concrete, especially for dry mixes. Workability means how easy concrete is to handle and compact. The test uses a cylindrical chamber, a standard slump cone, and a transparent disc-shaped rider mounted on a vibrating table. The cylindrical chamber measures nine and a half inches in diameter and eight inches in height. Concrete is placed into the slump cone in layers and compacted in the standard way. After the cone is removed, the concrete stays in the...

flow table test

The flow table test measures how far fresh concrete spreads, which helps assess workability. Workability means how easily concrete can flow and settle under its own weight. The method is useful for highly flowable concrete mixes. The test uses a flow table made from a wooden board with a steel plate on top. Together, the parts weigh 35 pounds. The board is hinged to a base and measures 27.6 inches on each side. A truncated cone mold is also used. It is 8 inches high, with an 8-inch base...

key terms and concepts

Measure concrete workability with the flow table test. Learn the mold size, jolting steps, and how spread is used to classify flowable mixes.

Concrete Spread Measured by Flow Table | JoVE K12

JoVE Core Civil Engineering provides a foundational exploration of essential construction materials in civil engineering, focusing on bricks, stones, steel, wood, and concrete through easy-to-understand animated videos. This collection covers the properties, manufacturing processes, and practical applications of these materials. Additionally, the accompanied science-in-action videos demonstrate the research experiments performed in laboratories.

civil engineering

Concrete Spread Measured by Flow Table

Description

Transcript

Tags